I need help on number 7

Astudent received the following grades last semester. find the student's semester grade point average. an a is algebra (3 credits), a b in history ( 3 credits), a in sociology ( 3 credits) a d in english ( 3credits) and a c in seminar ( 2credits). an a is worth 4 points, a b is worth 3 points a c is worth 2 points and a d is worth 1 point.

The angle of a triangle are given as 6x,(x-3), and (3x+7). find x then find the measures of the angles

Ineed with this problem 21 show steps